Life on Earth appears to be dominated by higher plants and animals. Yet an immense variety of microbial eukaryotes swarm in the foliage, grass, soil, bogs, ponds, streams, lakes, and oceans. These inconspicuous organisms are flagellates, algae, ciliates, sarcodines, slime molds, apicomplexans. This assemblage is generally termed the protists. Our course is to build a comprehensive picture of protistan diversity. The major steps of eukaryotic evolution will be in focus. By tracking phylogenetic affinities in protistan lineages we will elucidate the major branches on the tree of eukaryotic life.
Many protists are unicellular. This single cell is simultaneously a self-sufficient organism, which is able to sense, move, feed, and repulse an attack on its own. Therefore, protistan cells often demonstrate greater complexity of organelles, structures, and controls than the specialized cells of metazoan animals and higher plants. We will explore how free-living and parasitic unicells implement locomotion, food acquisition, digestion, osmotic regulation, and how they accomplish their life cycle. We also will look into how protists interact with the environment and manage to be biological success.
Within the six modules, we will speak of (1) what protists are, (2) flagellates, (3) sarcodines and slime molds, (4) ciliates, (5) apicomplexans and microsporidians, and (6) finally we will go over the modern phylogeny, will summarize life histories and discuss evolutionary trends in free-living and parasitic protists. This online course will have an optional on-campus extension, when the students have one week of practical exercises in the lab. Using light microscopy, they will observe, explore, and document live specimens and fixed mounts of naked and testate amoebas, foraminiferans, radiolarians, heliozoans, myxomycetes, flagellates, ciliates, gregarines, and coccidians.

Sergei Korsun

Zlatogursky Vasiliy

Ilya Udalov

Vladimir Klimov

Granovitch, Andrei

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The amoeboid form is widespread among the eukaryotes. Not only amoebas, but also the cells of a huge variety of protists, as well as many cell types of multicellular organisms are amoeboid. Check out an example of a human macrophage cell. It looks like a typical amoeba. But what does it mean? The amoeboid cells are different from the other forms of cells with non-stable, easily changing cell shape. The dynamic outgrowths of the cell surface performing locomotory or feeding functions are called pseudopodia. Let's quickly review the diversity of amoeboid protists. First of all, of course, these are so-called naked lobose amoebae. The cell membrane in these organisms of course surrounded by glycocalyx, which is typical for all the cells. But otherwise, it is usually naked. The lobose pseudopodia or lobopodia are thick and blunt and can be single in case of monopodial forms or multiple - polypodial forms. The slime moulds, belonging to the taxon Eumycetozoa are also amoebae and part of their lifecycle is represented just with tiny microscopic amoeboid cells. But they are also capable of forming huge multicellular aggregations - - pseudoplasmodia or giant multinucleated cells - - the true plasmodia, and finally to form fruiting bodies just like fungi do. Heterolobosean amoebae also form pseudopodia which are thick, blunt, but its formation is not gradual, but rather fast and spontaneous. This saltatory process is called eruptive movement, the type of amoeboid movement characterizing heteroloboseans. There are also amoeboid cells belonging to the group called Endomyxa. These cells also change its shape, but in this case, pseudopodia are long and thin. In this case, they're called filopodia. Mostly benthic marine protists called foraminiferans are also characterized with pseudopodia. This pseudopodia form a network, which it uses for feeding and locomotion. Multiple granules are moving along this network, which mostly represent food particles transported along this pseudopodial net. This type of pseudopodia is called granuloreticulopodia. The other prominent feature of this group is external shell, enclosing the cell body. Radiolarians - - the other amoeboid group are marine planktonic and, unlike foraminifera, have internal mineral skeletons composed of spicules or even solid internal perforated skeletons, having a variety of shapes. The last type of amoeboids, the heliozoans, and also radiolarians share the similar type of pseudopodia, the axopodia. Axopodia are straight, thin, and supported with a bundle of microtubules. But heliozoans, unlike radiolarians, do not have internal skeleton. Instead, they often have extracellular skeletal elements surrounding the organisms. In conclusion, it is necessary to emphasize that amoeboid protists do not represent a particular evolutionary lineage. Amoeboid cells can be found almost in all macroclusters across all the eukaryotic tree, and the term �amoeboid� just designates a particular type of cell organization, not a taxon of closely related organisms.